Internet protocol (IP) multimedia subsystem (IMS) is a new architecture developed so that IP networks can rapidly deploy new IP-based multimedia services. An evolved packet system (EPS) network is a next generation packet network architecture developed by the 3rd Generation Partnership Project (3GPP). EPS includes long term evolution (LTE) access networks and evolved packet core (EPC) networks (also referred to as system architecture evolution (SAE) networks). IMS over EPC networks is envisioned to be a next generation network architecture that supports a variety of access technologies and provides advanced IP multimedia services with seamless mobility.
An objective of call or connection admission control (CAC) is to determine whether an arriving call or connection with specified Quality of Service (QoS) requirements (e.g., bandwidth, packet loss probability, packet delay, jitter, etc.) should be admitted to the network. A new connection request is admitted, if the QoS requirements for the call can be satisfied without jeopardizing the QoS constraints of existing connections in the network. Otherwise, the request is rejected. The goal of CAC is to guarantee QoS for all connections in the network, while at the same time making efficient use of network resources (e.g., accommodating as many connections as possible).
The application of CAC to guarantee end-to-end QoS requirements of any connection can be quite complex. In a real network, such as an EPS network, control messages have to be sent along the end-to-end connection path to ascertain whether the QoS objective could be met without adversely affecting other connections in progress. Because of this, CAC is typically implemented only at a gateway for an originating call or connection. While this approach guarantees QoS requirements at the originating access node, it fails to guarantee any other nodes on a connection path beyond the originating node. In particular, there is no guarantee at a destination access node, which may be as important as the originating access node.